There is no doubt that 1 Corinthians 13:8 comes right out and says that tongues and prophecies and the supernatural sign gift of perfect knowledge shall cease.  The question of when is even answered...

When?  When that which is perfect is come.  So what is the "that which is perfect"?  It seems important to spell out precisely what the "that which is perfect" which  was to come at the time of the writing.  We have 3 possibilities for defining what the "that which is perfect" is.

1) It could mean Jesus:  But Jesus is a HE, not a that, and Jesus, even if He were referred to as a that (an object), He had already been here.

2) It could mean the Kingdom of Heaven which is still yet to come.

3) It could be the completed canon of scripture... the completed Bible.

Number 2 is eliminated because when Jesus comes with His Kingdom and we see Him face to face, hope is fulfilled and no longer abiding...

 Romans 8:24 For we are saved by hope: but hope that is seen is not hope: for
what a man seeth, why doth he yet hope for?
 25 But if we hope for that we see not, then do we with patience wait for it.

This leaves the final possibility, number 3.  When Paul wrote the passage of 1 Corinthians we did not have among us the completed written Word of God... not yet... they were still making it!  The Apostles were establishing the 1st and original Church, AND they were recording the Word of God.  God issued supernatural sign gifts in order to establish His Church and His Scriptures, but when the scriptures were completed (the canon of scripture), these sign gifts would no longer be needed because we would have among us the completed written Word of God.  So at the time of the writing, we had something among us which was in part.  This was the partially written Word of God.  But it would soon be complete!

1 Corinthians 13:13 And now ABIDETH faith, hope, charity, these three; but
the greatest of these is charity. (Paul say's that HOPE abideth, or in other words is PRESENTLY WITH US.  It continues to exist)  This cannot be at the time of the Kingdom, since Paul says at that point, HOPE will be realized and fulfilled. So there has to be a time when faith, hope and charity ABIDE, but TONGUES cease. It can only be when the Scriptures are completely written, and this has happened.

But KNOWLEDGE has not passed away yet, we still have that! Some will say.   Yes, but the knowledge Paul is speaking of here is that supernatural knowledge, another one of the supernatural sign gifts, it is obviously not common every day knowledge...

1Cor 12:8 For to one is given by the Spirit the word of wisdom; to another the word of knowledge by the same Spirit;